With development in the videoconferencing field, a user conference site has developed from one video camera, single channel of live video, and a single channel of live image to multiple cameras, multiple channels of live videos, and multiple channels of live images. The multiple video cameras, multiple channels of live videos, and multiple channels of live images at the same conference site are associated via a physical or logical relationship. When a conference subject needs to be discussed in a video conference, a video of conference content (for example, power point (PPT)) usually needs to be transmitted to each conference site such that the conference content may be displayed on a content display at a remote conference site. Implementation of the technology relies on a definition of a role of an auxiliary stream in the H.323 and H.239 protocols in the prior art. The protocols specify that an auxiliary stream is used to transmit an image of conference content, such as a PPT slide and a digital video disc (DVD) video.
An auxiliary stream form that is commonly used at present is a presentation (PRE) form. In the PRE form, a token management mode is used. A conference has only one presentation token, a conference site that obtains the token may send an auxiliary stream, and the auxiliary stream of the conference site that has the token is viewed at each conference site. When the conference site stops sending an auxiliary stream, the token may be released. When another conference site needs to send an auxiliary stream, the other conference site may obtain the token by requesting, and all applicants may request the token as long as the token is not locked. However, in an actual common conference, a general scenario is that a projected physical object is being viewed and a slide is being presented at the same time. When this scenario is extended to and applied in the videoconferencing field, it is required that a conference site that obtains a token is capable of simultaneously sending two auxiliary streams of images, and that the two auxiliary streams may be simultaneously broadcast to another conference site of the conference for viewing. The existing PRE form cannot meet the requirement of the foregoing scenario in which multiple auxiliary streams are managed by using a token.
To solve the foregoing problem, a solution for controlling multiple auxiliary streams is proposed in the prior art. In this solution, an extra presentation annex (PREAnnex) logic channel is extended to improve a single node's capability of sending an auxiliary stream such that a node that obtains a presentation token by means of application may send an extra auxiliary stream through the PREAnnex logic channel. Sending of multiple auxiliary streams may be implemented by using this method. However, a node may send multiple auxiliary streams only after the node obtains a token by means of application. When an auxiliary stream needs to be simultaneously sent at multiple conference sites in a conference, the solution still cannot be used to solve the problem.